The present invention relates to a method and a device for controlling impression-on operations for an intaglio printing press so as to print a sheet correctly from the first sheet after starting a printing operation.
FIG. 5 shows a conventional sheet-feed offset intaglio printing press for three-color printing. In the printing press, a sheet 1 is fed from a feeder 2 to an impression cylinder through a feeder board 3 and a paper feeding cylinder 4. On the other hand, each color ink is transferred on an outer periphery surface of a plate cylinder 8 through a duct roller 6a, 6b, 6c provided at a surrounding portion of the plate cylinder 8 and an intaglio ink roller 7a, 7b, 7c, respectively. The sheet 1 is printed by holding the sheet 1 between the plate cylinder 8 and the impression cylinder 5. A printed sheet 1 is discharged by a sheet discharging device 9 and piled at a pile portion 10.
In a sheet pass condition (in a printing operation), duct rollers 6a, 6b, 6c, the intaglio ink rollers 7a, 7b, 7c and the impression cylinder 5 are impressed on and these rollers (cylinders) are thrown off impression in a sheet stop condition (in a printing-off condition). An impression-on operation is operated after finishing a predetermined sensing process by a sensor 11 provided on the feeder board 3 after detecting an existence of the sheet 1. An irregular register, i.e. feeding over, bending, winding, double sheets feeding, corner folded sheet, a lack of a sheet and so on, of the sheet 1 at a down (up) stream of the feeder board 3 is detected by a irregular sheet sensor 12. A whole control is operated by a centralized control board 13.
In the sheet-feed offset intaglio printing press as shown in FIG. 5, after a printing operation is started, sheets from the first sheet to the second or third sheet can not be printed perfectly, so that such sheets are not utilized as a product. Such a problem is occurred every time after sheet supplying or sheet printing is reset after the sheet supplying stopped once. In the conventional printing press, there is a problem that an irregular ratio is relatively high.
It will be explained a reason why irregular printing is occurred with reference to an order of an impression-on operation. The first sheet 1 is fed to the feeder board 3 and then the impression-on sensor 11 detects an existence of the first sheet 1 at first. After the impression-on sensor 11 detecting the sheet 1, an operation for detecting a register condition is started by the irregular sheet sensor 12. When the first sheet 1 is approached to a front end of the feeder board 3, a condition of the sheet 1 is checked by the irregular sheet sensor 12 and then an impression-on operation is output from the centralized control board 13 after detecting the register set on a good condition. When an impression-on operation signal is output, the intaglio ink rollers 7a, 7b, 7c contact with the plate cylinder 8 at first and then the duct rollers 6a, 6b, 6c contacts with the intaglio ink rollers 7a, 7b, 7c, respectively and the impression cylinder 5 contacts with the plate cylinder 8 according to a degree of the sheet 1 feeding.
After the sheet 1 detected at a point A by the irregular sensor 12, it is necessary to feed the sheet 1 to a point B as a printing point by rotating a small diameter cylinder having a reference diameter, which is a diameter of paper feeding roll 4 and intaglio ink rollers 7a, 7b, 7c, 580.degree. as angle of rotation. On the other hand, after detecting the register condition of the sheet by the irregular sheet sensor 12, the intaglio ink roller 7a, 7b, 7c and the duct roller 6a, 6b, 6c are moved in order responding to the impression-on operation by rotating these rollers 300.degree. as angle of rotation. These rollers are rotated 1100.degree. as angle of rotation by transmitting each color ink to the point B, in which each color ink is transferred from a peripheral surface of the duct rollers 6a, 6b, 6c to a peripheral surface of the intaglio ink rollers 7a, 7b, 7c, respectively. It needs 1400.degree. angle of rotation at all. Therefor, the sheet 1 is arrived at the point B before the ink on the outer peripheral surface of the plate cylinder is arrived at the point B. In the printing press, the sheet 1 arrives at the point B before the plate cylinder on which a transferred ink is provided further rotates 820.degree. (1400.degree.-580.degree. ) so as to transmit the ink at the point B. It means 2 revolutions of the small diameter cylinder and 100.degree. as angle of rotation. The ink is not printed on the second sheet from the sheet supplying started. It begins to transfer the ink at an middle portion of the third sheet. The sheets from the fourth sheet can be utilized as a printing product and three sheets until the third sheet from the sheet suppling started are produced as an inferior product.
When the irregular sensor 12 detects an irregular register in a continuous printing operation of the printing press, the sheet supplying is stopped once. And then, an irregular sheet condition is adjusted and the sheet supplying is restarted so that the inferior products are produced again caused by the above described reason. The inferior products are piled on the pile portion 10 together with superior products. Therefor, a labour work is needed to pull out the inferior products from the piled sheet 1.
Upon considering the above prior art, the present invention provides a method and a device for controlling the impression-on operations of the intaglio printing press to print perfectly a sheet supplied from the first sheet.